1. Before slip inside your sleeping bag, fill a hot water bottle into it. This will make you warm and comfortable when you enter.
2. Remember sleeping bag does not generate heat. It will only trap human body heat. Warm up in the cold and let your blood circulate.
3. When you come back home, open your sleeping bag as soon as possible and hung it in a dry place out of direct sunshine for a day or so to make it dry completely.
4. Temporarily repair the break with tape before tearing or breaking a larger hole when outdoors. They should be completely repaired by patching or stitching later then.
5. Keep your sleeping bag away from the fire. Spark will easily burn out holes and the heat will melt them.